can't change password in Users Accounts applet

Steps to reproduce:
1) Go to Menu > System Settings > Users Accounts
2) For the default user, created with the system, click on the line of ..... next to where it says "Password"
3) enter current password as normal
4) type a random string of characters into the new password box. No matter how many you type, it was always says "not good enough" and refuse to let you change your password.